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Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques

Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques. UW-Madison NCRST-I Research Team Frank Scarpace, Alan Vonderohe, Teresa Adams (Investigators) Nick Koncz (Project Manager) Hongwei Zhu, Amar Padmanabhan, Jisang Park (Research Assistants).

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Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques

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  1. Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques UW-Madison NCRST-I Research Team • Frank Scarpace, Alan Vonderohe, Teresa Adams (Investigators) • Nick Koncz (Project Manager) • Hongwei Zhu, Amar Padmanabhan, Jisang Park (Research Assistants)

  2. Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques Objectives • Determine Differences among Results from the Various Techniques • Seek Methods for Improving Accuracies by Technology Integration • Seek Methods for Reducing Required Editing Time for Raw Softcopy Data

  3. Test Site: Highway Corridor Near Solon, IA

  4. Manual, LIDAR, and Softcopy Data Sets • Manual Photogrammetry Data Set Provided by Iowa DOT and CTRE: • Breaklines and Mass Points (~20-Meter Spacing) • Compiled on Analytical Stereoplotters from 1:4800 (nominal scale) photos • Expected Accuracy: 0.07-0.10m RMS

  5. Breaklines and Mass Points

  6. 1-Meter DEM Generatedfrom Manual Photogrammetry Data Set

  7. Manual, LIDAR, and Softcopy Data Sets • Softcopy Photogrammetry Data Set: • Same Photography as Manual Method • Same Camera Calibration • Same External Orientation Parameters • Film Diapositives Scanned at 15 Micrometers • 38 Photos in 3 Strips – 35 Stereo Models

  8. Manual, LIDAR, and Softcopy Data Sets • Softcopy Photogrammetry Data Set: • In-House Software • Resampled Epipolar Images • 1:32 Image Pyramids • Cross-Correlation • Least Squares Matching • Generates Irregular 1-Meter Spacing of Elevations

  9. Correlation Coefficients from a Single Model Red = 0.5-0.7 Yellow = 0.7-0.9 Green = > 0.9

  10. DEM by Softcopy Photogrammetry

  11. Manual, LIDAR, and Softcopy Data Sets • LIDAR Data Set: • Irregular 2-Meter Spacing of Elevations • Expected Accuracy: 0.15m RMS • Raw Data Were Edited, But Some Vegetation (e.g., Crops) Were Not Removed

  12. Part of the LIDAR Data Set

  13. Parts of the Three Data Sets Sample Comparisons and Results

  14. Comparison Methodology

  15. Sample Comparisons and Results Preliminary Results Indicate that Softcopy Data are at Least as Good as LIDAR when Compared to Manually-Extracted Data.

  16. Sample Comparisons and Results Mixed Land Use

  17. Sample Comparisons and Results Drainage Ditch

  18. Softcopy / LIDAR Integration Project Status Softcopy Extraction w/LIDAR (Initial Comparison)

  19. Softcopy / LIDAR Integration Project Status Softcopy Extraction w/LIDAR (Initial Comparison)

  20. Softcopy Editing Tools • Automated • Slope Filter (Spikes and Holes) • Manual (Stereo Viewing) • Point-by-Point • Polygon Constant Elevation • Polygon Planar Fit

  21. Manual Editing Tool Menu

  22. Manual Editing Polygon Selection Tool

  23. Manual Editing Set-to-Constant Elevation Tool

  24. One of the Stereo Pairs

  25. Raw Softcopy Data

  26. After Slope Filter

  27. After Slope Filter

  28. After Manual Editing

  29. After Manual Editing

  30. Effects of Slope Filter

  31. Conclusions • When Differenced with Manually-Derived Data, Softcopy Results (0.2-0.4m RMS) are Slightly Better than LIDAR (0.3-0.5m RMS). • When LIDAR is Used as First Approximation for Softcopy, Results are Mixed with Improvements of 20% (to 0.16m RMS) in Some Cases. • Slope Filter Improves Raw Softcopy Data by 10%. • Comparisons with Manually-Edited Softcopy Remain to be Done.

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